Executing Stream Segmentation with customized stream GRID

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05-17-2013 07:38 PM
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Yohanes_BudiSulistioadi
New Contributor
Hello,

I was trying to find the topic I was about to ask in the forum archive, but couldn't find proper case and/or answer. So I make a new thread here.
I am in process of modeling a medium sized watershed in the tropics (Indonesia). The best DEM available is 90m SRTM and among some ancillary data available are: river network (from 50K topographic maps), soil type and land use (few years back).

Challenge popped out when I wanted to match the delineated subbasins as resulted from either ArcHydro or GeoHMS Terrain Preprocessing commands, both resulting not reliable junctions and stream geometry, especially in the lower elevation. For your information, the landscape of this area is highly vary from steep hills, undulating highplains until very flat alluvial riverbanks combined with - almost always - inundated areas further from river center. As I had the "good" stream network along with all river names, I intended to process the hydrological model calculation according to those rivers. So what I did was:

  1. Follow through all crucial steps in terrain preprocessing in HEC-GeoHMS (DEM Reconditioning - Fill Sinks - Flow Direction - Flow Accumulation - Stream Definition) and then I stopped here to compare the str output with my existing stream map.

  2. Learning that the str Grid only contains "1" value for the main river where all the water should accumulate, I then edit (include generalized all meanders/curves) my existing stream map to match the starting point and all junctions defined by Hydro/Geo-HMS, then create field called "VALUE" and assign all of them with "1", then convert it to raster and renamed it to str1

  3. Assuming the file structure already been matched between the two (str : arc defined stream and str1 : edited existing stream) I then continue the terrain pre-processing with Stream Segmentation for "str1" grid that I just created. FYI the existing stream polyline contains ONLY 58 segments/feature before I converted to grid.

  4. When investigating the result, I surprised since the str1lnk resulted from stream segmentation based on the "real" stream gives me very large value range (from 1 to 9970) compared to the strlnk grid resulted from artificial stream (from 1 to 67)

  5. Whenever I continue with the next steps (Catchment Grid Delineation - Catchment Polygon Processing - Adjoint Catchment Processing - etc) GeoHMS always gave me TONS of small catchments, which makes it difficult to manually merge them in GeoHMS

The questions are:

  • Have anybody ever tried this approach before?

  • If this approach is not a good one, how to modify the sub-basins resulted from automatic process in Hydro/GeoHMS according to the real ones?

For anyone interested to help and want to try to run the process with the dataset, I put them in dropbox linked below:
Dataset

Thank you in advance

Budi Sulistioadi
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ChristineDartiguenave
Esri Contributor
The objective of Catchments/AdjointCatchments/etc. is not to mimic the real world but to create a set of preprocessed data allowing fast watershed delineations. If you want to create a set of "catchments" (really subwatersheds) that mimic the real world, you can do this by creating the stream link grid and str grid based on your input stream instead of using a cell threshold.

You could use the following steps (assuming a dendritic terrain where everything flows nicely downstream) to burn in your streams and create one catchment for each of your stream segments:

1. Create Drainage Line Structures -> based on you streams, this tool will generate the streamlink grid and drainage line as a rasterized version of your input streams.
2. DEM Reconditioning (burning in the streams - you can use drainageline which is already rasterized as input)
3. Fill Sinks (assuming a dendritic terrain)
4. Flow Direction
5. Adjust Flow Direction in Streams
6. Catchment Grid Delineation (based on stream link)
7. Catchment Polygon Processing

Christine Dartiguenave
Esri Water Resources Team

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MarkBoucher
Occasional Contributor III
Budi,

I downloaded and processed your data.

I think you shouldn't modify the str or strlnk raster. By modifying either of these layer you are making them inconsistent with the fdr layer. I don't think that is a good thing. You should modify the um_mainflow_u50n (stream) layer. This layer dictated where the streams go (the fdr layer). Modify the stream layer and reprocess from your step 1.

Things to make the process less painful:

  • If you are working on a network, move the data to your local PC. It will process much faster.

  • Build a model in Model Builder. There is a pre-made model in the ArcHydro tool box. You can copy that to a toolbox in your project directory and run it. It will modify the model automatically to make the layers and rasters be saved to the right folders and geodatabases. If you modify the stream layer, you can run the model again instead of having to use the menus.

Hope this helps.
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ChristineDartiguenave
Esri Contributor
The objective of Catchments/AdjointCatchments/etc. is not to mimic the real world but to create a set of preprocessed data allowing fast watershed delineations. If you want to create a set of "catchments" (really subwatersheds) that mimic the real world, you can do this by creating the stream link grid and str grid based on your input stream instead of using a cell threshold.

You could use the following steps (assuming a dendritic terrain where everything flows nicely downstream) to burn in your streams and create one catchment for each of your stream segments:

1. Create Drainage Line Structures -> based on you streams, this tool will generate the streamlink grid and drainage line as a rasterized version of your input streams.
2. DEM Reconditioning (burning in the streams - you can use drainageline which is already rasterized as input)
3. Fill Sinks (assuming a dendritic terrain)
4. Flow Direction
5. Adjust Flow Direction in Streams
6. Catchment Grid Delineation (based on stream link)
7. Catchment Polygon Processing

Christine Dartiguenave
Esri Water Resources Team
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Yohanes_BudiSulistioadi
New Contributor
Mark, Christine,

Thank you very much for your inputs. Will try your suggestions and report back to this thread.
Very much appreciated.

Budi
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Yohanes_BudiSulistioadi
New Contributor
Christine,

I finally had a success in modifying ArcHydro standard stream segmentation steps by following your suggestion. Thank you very much and it might be worth to note that your suggestion is not exist in any other tutorials I could find (either from ESRI, Dr Maidment or Dr Merwade). So that may be a good point to add to the forthcoming tutorials.

Thanks again!
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